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Abstract:

A handheld engine-driven cutter is provided with a disk blade and a main
body that drives the disk blade. The main body comprises a four-stroke
engine, an oil supplying opening from which engine oil is supplied, and
an oil exhausting opening from which the engine oil is exhausted. In this
engine cutter, the oil supplying opening and the oil exhausting opening
are both disposed on one side of the main body where one end of a driving
axis of the four-stroke engine is located.

Claims:

1. A handheld engine-driven cutter comprising: a disk blade; and a main
body that drives the disk blade, the main body comprising: a four-stroke
engine; an oil supplying opening from which engine oil is supplied; and
an oil exhausting opening from which the engine oil is exhausted, wherein
the oil supplying opening and the oil exhausting opening are disposed on
one side of the main body.

2. A handheld engine-driven cutter as in claim 1, wherein the main body
further comprises a fuel supplying opening from which fuel is supplied,
and the fuel supplying opening is also disposed on the one side of the
main body.

3. A handheld engine-driven cutter as in claim 1, wherein the main body
further comprises a starter member that is operated by a user to start
the four-stroke engine, and the starter member is also disposed on the
one side of the main body.

4. A handheld engine-driven cutter as in claim 1, wherein the main body
further comprises a transmission mechanism that supports the disk blade
and transmits torque from the four-stroke engine to the disk blade, and
the transmitting mechanism is also disposed on the one side of the main
body.

5. A handheld engine-driven cutter as in claim 2, wherein the main body
further comprises a starter member that is operated by a user to start
the four-stroke engine, and the starter member is also disposed on the
one side of the main body.

6. A handheld engine-driven cutter as in claim 5, wherein the main body
further comprises a transmission mechanism that supports the disk blade
and transmits torque from the four-stroke engine to the disk blade, and
the transmitting mechanism is also disposed on the one side of the main
body.

7. A handheld engine-driven cutter as in claim 3, wherein the main body
further comprises a transmission mechanism that supports the disk blade
and transmits torque from the four-stroke engine to the disk blade, and
the transmitting mechanism is also disposed on the one side of the main
body.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to Japanese Patent Application No.
2010-46694 filed on Mar. 3, 2010, the contents of which are hereby
incorporated by reference into the present application.

TECHNICAL FIELD

[0002] The present invention relates to a handheld engine-driven cutter
that drives a disk blade by an engine.

DESCRIPTION OF RELATED ART

[0003] Japanese Patent Application Publication No. 2007-528792 discloses a
handheld engine-driven cutter. The engine-driven cutter comprises a disk
blade and an engine that drives the disk blade, and is used e.g. for
cutting concrete and steel materials at a building site. A two-stroke
engine is used as the foregoing engine. The two-stroke engine is
advantageous over other types of engines in that its structure is simple
and its size is small. Thus, the two-stroke engine is used in the
handheld engine-driven cutter for downsizing and cost reduction.

[0004] Nevertheless, the two-stroke engine has a problem in that its
emission of unburned gas is high, and its adverse effect on the natural
environment is relatively great. Demands for environmental performance
are also increasing with handheld engine-driven cutters, and it is
difficult for the conventional products adopting the two-stroke engine to
satisfy the high level of environmental performance that is being
demanded.

BRIEF SUMMARY OF INVENTION

[0005] In light of the foregoing circumstances, a use of a four-stroke
engine in substitute for the two-stroke engine in the handheld
engine-driven cutter may be considered. With the four-stroke engine,
since its intake port and exhaust port are respectively opened and closed
with a valve operating mechanism, there is an advantage in that the
emission of unburned gas is low and it is energy-efficient in comparison
to the two-stroke engine in which the ports are opened and closed
respectively with a piston. In particular, with a separate lubrication
system four-stroke engine, since a large amount of engine oil is subject
to cyclic use within the engine and the amount of engine oil that is
consumed together with fuel is extremely small, the environmental
performance can be improved even further.

[0006] However, with the separate lubrication system four-stroke engine,
unlike a mixed lubrication system two-stroke engine or a four-stroke
engine that uses fuel with engine oil mixed therein, the engine oil needs
to be supplied separately from the fuel. Moreover, the engine oil needs
to be replenished and replaced in an adequate frequency. Thus, if the
separate lubrication system four-stroke engine is adopted in the
engine-driven cutter, it is anticipated that a user who has been using
the conventional product will have trouble or even be unsuccessful in
replacing the engine oil due to inexperience.

[0007] Accordingly, an object of this invention is to provide teachings
for facilitating the replacement of the engine oil in the engine-driven
cutter mounted with the four-stroke engine.

[0008] In one aspect of the present teachings, a handheld engine-driven
cutter comprises a disk blade, and a main body that drives the disk
blade. The main body comprises a four-stroke engine, an oil supplying
opening from which engine oil is supplied, and an oil exhausting opening
from which the engine oil is exhausted. This engine-driven cutter has the
oil supplying opening and the oil exhausting opening disposed on one side
of the main body.

[0009] If the oil supplying opening and the oil exhausting opening are
both disposed on the same side of the main body, the user can replace the
engine oil without having to change the direction of the engine-driven
cutter or change one's position relative to the engine-driven cutter.
Moreover, since the oil supplying opening and the oil exhausting opening
can be visually confirmed simultaneously, it is possible to prevent a
mistake such as continuing to supply the engine oil from the oil
supplying opening while forgetting to close the oil exhausting opening.
If the oil supplying opening and the oil exhausting opening are disposed
on one side of the main body, the user can comfortably perform operations
without having to mind the oil supplying opening or the oil exhausting
opening by using the engine-driven cutter while being in a position on
the other side of the main body.

[0010] According to the aforementioned structure, it is possible to
realize an engine-driven cutter mounted with a four-stroke engine in
which the replacement of the engine oil is facilitated (easy to
understand). Moreover, it is possible to realize an engine-driven cutter
that can be used by the user comfortably without having to mind the
existence of the oil supplying opening and the oil exhausting opening.

BRIEF DESCRIPTION OF DRAWINGS

[0011]FIG. 1 shows a view of an engine-driven cutter from a right side
(driving side).

[0012]FIG. 2 shows a plan view of the engine-driven cutter from above.

[0014] FIG. 4 is a partial cross sectional view of a main body of the
engine-driven cutter.

[0015] FIG. 5 shows an assembly structure of a casing main body and a
filter bracket and a filter cover.

[0016] FIG. 6 is another view of the assembly structure of the casing main
body and the filter bracket and the filter cover from a different
direction from that of FIG. 5.

[0017] FIG. 7 shows an assembly structure of a filter bracket and a
carburetor and a carburetor mount.

[0018] FIG. 8 shows a positional relationship of a carburetor arm and a
recess portion of the carburetor mount.

[0019] FIG. 9 shows a connection structure of the filter bracket and the
carburetor and the carburetor mount.

[0020] FIG. 10 shows the connection structure of the filter bracket and
the carburetor and the carburetor mount from a different direction from
that of FIG. 9.

[0021] FIG. 11 shows a state where an oil separator and a breathing tube
are mutually connected via a through hole of a seal member,

[0022] FIG. 12 shows an assembly structure of a throttle lever and a
switch lever.

[0023] FIG. 13 is an exploded view of an assembly structure of the
throttle lever and the switch lever.

[0024] FIG. 14 shows a guard from the right side.

[0025] FIG. 15 shows the guard from a front side.

[0026] FIG. 16 shows the guard from a bottom side.

[0027] FIG. 17 is a cross sectional view of line XVII-XVII in FIG. 14.

[0028] FIG. 18 is a cross sectional view of line XVIII-XVIII in FIG. 16.

[0029] FIG. 19 shows a state where the engine-driven cutter is fully
angled towards a surface of a workpiece.

DETAILED DESCRIPTION OF INVENTION

[0030] In one embodiment of the present teachings, the main body may
further comprise a fuel supplying opening from which fuel is supplied. In
the foregoing case, preferably, the fuel supplying opening is also
disposed on the one side of the main body as with the oil supplying
opening and the oil exhausting opening. According to this structure, the
user visually confirms the oil supplying opening and the fuel supplying
opening simultaneously. Consequently, it is possible to prevent the user
from erroneously supplying the fuel to the oil supplying opening or
erroneously supplying the engine oil to the fuel supplying opening. In
addition, the user can comfortably perform operations without having to
mind the existence of the oil supplying opening, the oil exhausting
opening, and the fuel supplying opening by using the engine-driven cutter
while being in a position on the other side of the main body.

[0031] In one embodiment of the present teachings, the main body may
further comprise a starter member that is operated by the user to start
the four-stroke engine. In the foregoing case, preferably, the starter
member is also disposed on the one side of the main body as with the oil
supplying opening and the oil exhausting opening. According to the
foregoing structure, the user can comfortably perform operations without
having to mind the existence of the oil supplying opening, the oil
exhausting opening, and the starter member by using the engine-driven
cutter while being in the position on the other side of the main body.

[0032] In one embodiment of the present teachings, the main body may
further comprise a transmission mechanism that supports the disk blade
and transmits torque of the four-stroke engine to the disk blade. In the
foregoing case, preferably, the transmitting mechanism is also disposed
on the one side of the main body as with the oil supplying opening and
the oil exhausting opening. According to the foregoing structure, the
user can comfortably perform operations without having to mind the
existence of the oil supplying opening, the oil exhausting opening, and
the transmitting mechanism by using the engine-driven cutter while being
in the position on the other side of the main body.

[0033] Representative, non-limiting examples of the present invention will
now be described in further detail with reference to the attached
drawings. This detailed description is merely intended to teach a person
of skill in the art further details for practicing preferred aspects of
the present teachings and is not intended to limit the scope of the
invention. Furthermore, each of the additional features and teachings
disclosed below may be utilized separately or in conjunction with other
features and teachings to provide improved engine-driven cutters.

[0034] Moreover, combinations of features and steps disclosed in the
following detail description may not be necessary to practice the
invention in the broadest sense, and are instead taught merely to
particularly describe representative examples of the invention.
Furthermore, various features of the above-described and below-described
representative examples, as well as the various independent and dependent
claims, may be combined in ways that are not specifically and explicitly
enumerated in order to provide additional useful embodiments of the
present teachings.

[0035] All features disclosed in the description and/or the claims are
intended to be disclosed separately and independently from each other for
the purpose of original written disclosure, as well as for the purpose of
restricting the claimed subject matter, independent of the compositions
of the features in the embodiments and/or the claims. In addition, all
value ranges or indications of groups of entities are intended to
disclose every possible intermediate value or intermediate entity for the
purpose of original written disclosure, as well as for the purpose of
restricting the claimed subject matter.

Embodiment

[0036] Examples of an engine-driven cutter are explained below with
reference to the appended drawings. FIG. 1 is a side view of an
engine-driven cutter 10, and FIG. 2 is a plan view of the engine-driven
cutter 10. Moreover, FIG. 3 is a cross sectional view of line in FIG. 1.
The engine-driven cutter 10 comprises a disk blade 12, and a main body 14
that drives the disk blade 12. The disk blade 12 can cut lithic materials
and metal materials, and the engine-driven cutter 10 is used e.g. for
cutting concrete and steel materials at a building site.

[0037] As shown in FIG. 1 and FIG. 2, when the engine-driven cutter 10 is
mounted on a horizontal plane H, the disk blade 12 is positioned on one
side of the horizontal direction relative to the main body 14. In the
ensuing explanation, a state where the engine-driven cutter 10 is mounted
on the horizontal plane H is used as the reference, and one side of the
horizontal direction where the disk blade 12 is positioned relative to
the main body 14 is referred to as a front side, and the opposite
direction thereof is referred to as a rear side. Moreover, the vertical
upward direction is simply referred to as an upper side and the vertical
downward direction is simply referred to as a lower side. In addition, as
shown in FIG. 2, one side of the horizontal direction that is
perpendicular to the front-back direction is referred to as a left side
and the other side of the horizontal direction perpendicular to the
front-back direction is referred to as a right side. For example, the
disk blade 12 is positioned in front of the main body 14, and its
rotating axis extends in the left-right direction and perpendicular to
the horizontal plane H at the upper side of the horizontal plane H.

[0038] The main body 14 is provided with a front handle 16 and a rear grip
28. The front handle 16 is formed with a pipe material, and, in addition
to being a handle to be grasped by the user, it also functions as a frame
for ensuring the strength of the main body 14. The front handle 16
extends from the upper side to the left side of the main body 14 at the
front part of the main body 14. The rear grip 28 is provided in the lower
rear part of the main body 14. The rear grip 28 extends in a loop shape
from the main body 14. The rear grip 28 is provided with an operation
switch such as a throttle lever 30. Moreover, the lower part of the rear
grip 28 is provided with a rear foot part 38.

[0039] Normally, the user grasps the front handle 16 with one's left hand,
and grasps the rear grip 28 with one's right hand to hold the
engine-driven cutter 10. The user moves the engine-driven cutter 10
relative to the workpiece and cuts the workpiece with the disk blade 12.
As described above, the engine-driven cutter 10 of this embodiment is a
handheld engine-driven cutter that is held by the user. Here, when the
user holds the engine-driven cutter 10 as described above, the user is
positioned on the left side of the main body 14. Normally, since the user
is positioned on the left side of the engine-driven cutter 10, the left
side of the engine-driven cutter 10 is also referred to as the user side.

[0040] The main body 14 comprises an engine 18 that drives the disk blade
12. The engine 18 is a four-stroke reciprocating engine. With the
four-stroke engine, since an intake port and an exhaust port are
respectively opened and closed with a valve operating mechanism, there is
an advantage in that the emission of unburned gas is low and it is
energy-efficient (low fuel consumption) in comparison to a two-stroke
engine in which such ports are opened and closed respectively with a
piston. Since the engine-driven cutter 10 adopts the four-stroke engine
18, its environmental performance is considerably improved.

[0041] Since the engine 18 is a separate lubrication system four-stroke
engine, unlike a mixed lubrication-type two-stroke engine. The engine oil
needs to be supplied separately from the fuel. Moreover, the engine oil
needs to be replenished and replaced at an adequate frequency. Thus, the
engine 18 is provided with an oil supplying opening 18a to which the
engine oil is fed, and an oil exhausting opening 18b for exhausting the
engine oil.

[0042] Note that the engine 18 is not limited to the separate lubrication
system four-stroke engine, and it may also be a mixed lubrication system
four-stroke engine. However, the separate lubrication system four-stroke
engine has an advantage in that it yields superior environmental
performance in comparison to the mixed lubrication system four-stroke
engine, since a large amount of engine oil is subject to cyclic use in
the engine, and the amount of engine oil that is consumed together with
the fuel is extremely small. Moreover, running costs to be borne by a
user can also be reduced since the consumption of the engine oil is
reduced. Furthermore, if the mixed lubrication system four-stroke engine
is employed in a case where the engine-driven cutter 10 is not used for a
long period of time, the fuel in the carburetor will evaporate causing
only the engine oil to remain therein, and the carburetor may become
clogged. With respect to this point, by adopting the separate lubrication
system four-stroke engine, the effect of being able to avoid this kind of
problem can also be expected.

[0043] The main body 14 comprises a cutter arm 56 mounted on the disk
blade 12. The cutter arm 56 is provided on the right side of the main
body 14, and extends toward the front side of the main body 14. As shown
in FIG. 3, the cutter arm 56 comprises a first plate 56b fixed to the
engine 18 and a second plate 56c fixed to the first plate 56b, and the
second plate 56c is provided with a tool shaft 56e for rotatably
supporting the disk blade 12.

[0044] Moreover, the cutter arm 56 comprises a drive pulley 56a fixed to
the driving axis (crank shaft) 18c of the engine 18, a driven pulley 56f
fixed to the tool shaft 56e, and a transmission belt 56d placed across
the drive pulley 56a and the driven pulley 56f. Consequently, torque
output by the engine 18 is transmitted to the tool shaft 56e, and the
disk blade 12 is rotatably driven by the engine 18. Accordingly, the
cutter arm 56 is also a transmission mechanism for transmitting the
torque output by the engine 18 to the disk blade 12. The right side of
the main body 14 to which the cutter arm 56 as the transmitting mechanism
is provided is generally referred to as the driving side. Here, the
position for mutually fixing the first plate 56b and the second plate 56c
is adjustable, and the tension of the transmission belt 56d can be
adjusted. Note that the driving axis 18c of the engine 18 and the tool
shaft 56e are mutually parallel, and they both extend in the left-right
direction. Moreover, the cutter arm 56 is provided with a disk blade
cover 58 for covering the disk blade 12.

[0045] The main body 14 comprises a recoil starter 44 for the user to
start the engine 18. The recoil starter 44 is provided on the right side
of the main body 14, and provided above the cutter arm 56. As shown in
FIG. 3, the driving axis 18c of the engine 18 extends by passing through
the drive pulley 56a, and the recoil starter 44 is connected to the
distal end of the driving axis 18c. The recoil starter 44 is provided
with a starter lever 42 to be operated by the user. When the user pulls
the starter lever 42, the driving axis 18c of the engine 18 rotates and
the engine 18 is started.

[0046] The main body 14 comprises a guard 50. The guard 50 is provided on
the lower front side of the main body 14. The lower front side of the
main body 14 is a position where chips of a workpiece scatter from the
disk blade 12, and the guard 50 repels the scattered chips of the
workpiece toward the lower side of the main body 14. Consequently, the
chips of the workpiece that collide with the main body 14 are prevented
from being repelled toward the user. Moreover, the guard 50 is provided
with a pair of rollers 52 and a front leg portion 54. The pair of rollers
52 are positioned more toward the front side than the front leg portion
54. When the user raises the rear grip 28 to the upper side, the pair of
rollers 52 contact the surface of the workpiece and become a fulcrum for
angling the engine-driven cutter 10 towards the workpiece. Note that the
structure of the guard 50 is explained in detail later.

[0047] The main body 14 comprises a casing 20. The casing 20 is formed
from a resin material. The casing 20 comprises a casing main body 26, a
filter cover 24, and a top cover 22. The top cover 22 is fixed to the
filter cover 24, and the filter cover 24 is fixed to the casing main body
26. A part of the casing main body 26 is a fuel tank for storing the fuel
of the engine 18, and is provided with a fuel supplying opening 40 for
supplying the fuel. Moreover, the casing main body 26 is integrally
formed with the rear grip 28 described above, and the internal space of
the rear grip 28 also constitutes a part of the fuel tank.

[0048] FIG. 4 shows the right side of the main body 14. Note that, in FIG.
4, a part thereof is a cross section, and the structure inside the casing
20 is shown. As shown in FIG. 4, with the engine-driven cutter 10, the
oil supplying opening 18a and the oil exhausting opening 18b are both
provided on the right side of the main body 14. As described above, if
the oil supplying opening 18a and the oil exhausting opening 18b are both
provided on the same side of the main body 14, the user can replace the
engine oil without having to change the direction of the engine-driven
cutter 10 or change one's position relative to the engine-driven cutter
10. Moreover, since the oil supplying opening 18a and the oil exhausting
opening 18b can be visually confirmed simultaneously, it is possible to
prevent a mistake such as continuing to supply the engine oil from the
oil supplying opening 18a while forgetting to close the oil exhausting
opening 18b. In addition, since the oil supplying opening 18a and the oil
exhausting opening 18b are disposed on the right side (driving side) of
the main body 14, the oil supplying opening 18a and the oil exhausting
opening 18b will not get in the way of the user positioned on the
opposite left side (user side).

[0049] In addition to the above, with the engine-driven cutter 10, the
recoil starter 44, the starter lever 42, and the fuel supplying opening
40 are also provided on the right side (driving side) of the main body
14. Accordingly, existence of the recoil starter 44, the starter lever
42, and the fuel supplying opening 40 will not get in the way of the user
positioned on the opposite left side (user side). Accordingly, with the
engine-driven cutter 10 of this embodiment, the oil supplying opening
18a, the oil exhausting opening 18b, the recoil starter 44, the starter
lever 42, and the fuel supplying opening 40 are all provided on the right
side (driving side) of the main body 14 where the cutter arm 56 is
positioned. Accordingly, as shown in FIG. 2, a large concavo-convex does
not exist on the left side (user side) of the main body 14 in comparison
to the right side (driving side) of the main body 14. Consequently, the
user can comfortably perform operations without having to mind the
concavo-convex of the main body 14.

[0050] The internal structure of the casing 20 is now explained. As shown
in FIG. 4, a flow path shown with arrow F in FIG. 4 is formed in the
casing 20, and the structure is such that the air introduced from the
intake window 22a of the top cover 22 passes through the casing 20 and is
supplied to the engine 18 via an intake connecting tube 62. The casing 20
is internally provided with a pre-filter 68, a main filter 70, and a
carburetor 74 along the foregoing flow path F. The pre-filter 68 is
positioned between the top cover 22 and the filter cover 24, and the main
filter 70 is positioned between the filter cover 24 and the casing main
body 26. Thus, the pre-filter 68 is positioned at the upper side of the
main filter 70 in a state where the engine-driven cutter 10 is mounted on
the horizontal plane H. The air introduced from the intake window 22a
passes through the pre-filter 68 and the main filter 70 in that order,
and the dust contained therein is removed (or filtered). Here, after the
air passes through from the lower side to the upper side of the
pre-filter 68, it flows along the inner surface of the top cover 22 and
the filter cover 24, and passes through the main filter 70 after changing
its direction of flow approximately 270 degrees.

[0051] The air that passed through the main filter 70 subsequently passes
through the carburetor 74. The carburetor 74 mixes the air that passed
through the main filter 70 with the fuel. The carburetor 74 is a
general-purpose carburetor, and includes a throttle valve, a check valve,
an air vent and the like. The air that was mixed with the fuel in the
carburetor 74 (so-called air-fuel mixture) passes through the intake
connecting tube 62 is supplied to the engine 18. Note that the intake
connecting tube 62 is positioned outside of the casing 20. Moreover, FIG.
4 shows the breathing tube 64 at the upper side of the intake connecting
tube 62. The breathing tube 64 extends from the engine 18, and is
connected to an oil separator 82 described later. Note that the breathing
tube 64 is a pipeline for eliminating blow-by gas discharged inside the
locker cover within the engine 18, and is connected to a circulatory path
of the engine oil including a crank casing within the engine 18.

[0052] The engine-driven cutter 10 of this embodiment adopts the
four-stroke engine 18. With the four-stroke engine, the intake port is
provided in the cylinder head, and the carburetor 74 connected to the
intake port is positioned relatively on the upper side. Thus, if the main
filter 70 is positioned at the upper side of the carburetor 74, the main
filter 70 will protrude considerably toward the upper side relative to
the engine 18, and the height of the engine-driven cutter 10 is
increased. Thus, with the engine-driven cutter 10 of this embodiment, as
shown in FIG. 4, the main filter 70 and the carburetor 74 are arranged to
align on a straight line along the direction of flow of the air passing
through the main filter 70 and the carburetor 74. Specifically, the
carburetor 74 is positioned at the rear side of the engine 18 and the
main filter 70 is positioned at the rear side of the carburetor 74.
According to this kind of arrangement and structure, even if the
four-stroke engine 18 is adopted, the height of the engine-driven cutter
10 can be kept relatively small.

[0053] As shown in FIG. 4, with the engine-driven cutter 10 of this
embodiment, a relatively large main filter 70 is adopted, and a part of
the main filter 70 is protruding toward the upper side of the rear grip
28. Consequently, the rear surface of the casing 20 (portion of the
filter cover 24) is also protruding in a convex shape at the upper side
of the rear grip 28. Accordingly, if a part or the entirety of the main
filter 70 is disposed to protrude up reaching the upper side of the rear
grip 28, a large main filter 70 can be mounted. As a result of mounting
the large main filter 70, the main filter 70 does not clog easily, and
the user needs to clean the main filter 70 less frequently. Note that,
even if the rear surface of the casing 20 protrudes in the convex shape
at the upper side of the rear grip 28, it will not interfere with the
user's hand that will grasp the rear grip 28. If such interference
becomes a problem, the angle of the rear grip 28 may be adjusted.

[0054] Note that, with the conventional engine-driven cutter, the
two-stroke engine is adopted. With the two-stroke engine, the intake port
is provided in the cylinder block and the carburetor connected to the
intake port is positioned relatively low. Consequently, with the
conventional engine-driven cutter, the main filter 70 is disposed at the
upper side of the carburetor 74, and the downsizing of the engine-driven
cutter is thereby being sought (for example, refer to Japanese Patent
Application Publication No. 2007-528792).

[0055] As shown in FIG. 4, with the engine-driven cutter 10, when the
engine-driven cutter 10 is mounted on the horizontal plane H, the design
is such that a central axis C of the cylinder of the engine 18 is angled
towards the carburetor 74 relative to a vertical direction V. If the
engine 18 is disposed as described above, the carburetor 74 and the main
filter 70 connected to the engine 18 can be positioned even lower.
Consequently, the height of the engine-driven cutter 10 can be reduced.
In addition, since the four-stroke engine includes a valve operating
mechanism above the cylinder head and the oil pan below the crank casing,
its height is relatively great in comparison to the two-stroke engine,
and there is a possibility that this may cause the enlargement of the
engine-driven cutter 10. With respect to this point also, if the engine
18 is angled and positioned as described above, the engine-driven cutter
10 can be designed to be compact.

[0056] As shown in FIG. 4 and FIG. 5, a filter bracket 72 is provided
between the main filter 70 and the carburetor 74. The filter bracket 72
guides the air that passed through the main filter 70 to the carburetor
74. The filter bracket 72 is fixed to the casing main body 26, and
retains the main filter 70 at a fixed position.

[0057] As shown in FIG. 5 and FIG. 6, the filter bracket 72 is fixed to
the casing main body 26 together with the filter cover 24 with a mutual
bolt 84. According to this structure, it is possible to simplify the
structure and reduce the number of components in comparison to the
structure where the filter bracket 72 and the filter cover 24 are
separately fixed, and the further downsizing of the engine-driven cutter
10 can be sought. In addition, the assembly process of the engine-driven
cutter 10 can be simplified. Note that, although not shown in FIG. 4 and
FIG. 5, as described later, the carburetor 74, the carburetor mount 66,
the intake connecting tube 62 and the like are assembled to the filter
bracket 72 in advance. Moreover, a main filter 70 is disposed between the
filter cover 24 and the filter bracket 72 upon the assembly thereof.

[0058] As shown in FIG. 4, the casing 20 includes a carburetor mount 66 to
which the carburetor 74 is fixed. The carburetor mount 66 is mounted on a
notch portion 26a of the casing main body 26 shown in FIG. 4 and FIG. 5,
and configures a part of the outer wall of the casing 20. The carburetor
mount 66 is mounted on the casing main body 26 via a seal member 76. The
seal member 76 is an elastic member formed with a material with
elasticity. In this embodiment, as one example, the seal member 76 is
formed with a polymer material (more specifically a rubber material). The
carburetor mount 66 can be displaced relative to the casing main body 26
based on the deformation of the seal member 76.

[0059] FIG. 7 shows a group of components that is assembled to the
carburetor mount 66. As shown in FIG. 7, the filter bracket 72 and the
intake connecting tube 62 are assembled to the carburetor mount 66 in
addition to the carburetor 74. Here, the filter bracket 72 and the
carburetor 74 and the carburetor mount 66 and the intake connecting tube
62 are mutually assembled with a mutual bolt 80. Note that a gasket 78 is
disposed between the filter bracket 72 and the carburetor 74 upon
assembling the foregoing group of components, and a seal member 76 is
disposed at the peripheral edge of the carburetor mount 66.

[0060] As shown in FIG. 7, the carburetor mount 66 includes two supporting
beam portions 66b protruding toward the carburetor 74. The supporting
beam portions 66b support the carburetor 74 from the bottom and retain
the carburetor 74 at the assembly position upon assembling the filter
bracket 72 to the carburetor mount 66 with the carburetor 74 interposed
therebetween. As a result of the supporting beam portion 66b retaining
the carburetor 74, the operator to perform such assembly can easily
perform the assembly process without having to support the carburetor 74
with one's hand.

[0061] As shown in FIG. 7, the carburetor mount 66 is formed with a recess
portion 66c. The recess portion 66c is formed on a surface that is
positioned on the side of the carburetor 74. As shown in FIG. 8, the
recess portion 66c faces the arm 74c that opens and closes the throttle
valve of the carburetor 74, and prevents the arm 74c from contacting the
carburetor mount 66. As described above, as a result of forming the
recess portion 66c in a range facing the arm 74c, the space between the
carburetor mount 66 and the filter bracket 72 can be designed to be
narrow, and the downsizing of the engine-driven cutter 10 can thereby be
sought.

[0062] The filter bracket 72 is fixed to the carburetor mount 66 with the
carburetor 74 interposed therebetween as shown in FIG. 7, and thereafter
fixed to the casing main body 26 as shown in FIG. 5 and FIG. 6. Here, the
carburetor mount 66 is mounted on the notch portion 26a of the casing
main body 26 via the seal member 76. Accordingly, even if there is a
dimension error in the filter bracket 72, the casing main body 26, and
the carburetor mount 66, the filter bracket 72 can be properly fixed to
the casing main body 26 by the carburetor mount 66 subordinately
displacing in accordance with the casing main body 26 to compensate for
the dimension error.

[0063] FIG. 9 and FIG. 10 show a connection relationship concerning a flow
path constituted of the filter bracket 72, the carburetor 74, the
carburetor mount 66, and the seal member 76. As shown in FIG. 9 and FIG.
10, when the filter bracket 72 is assembled to the carburetor mount 66
with the carburetor 74 intervening therebetween, an opening 72a of the
filter bracket 72 is connected to an opening 66a of the carburetor mount
66 via a main path 74a of the carburetor 74.

[0064] As shown in FIG. 9 and FIG. 10, an oil separator 82 is integrally
formed to the filter bracket 72. Moreover, the oil separator 82 is
protruding from the filter bracket 72 towards the carburetor 74. In a
case where the structure is such that the oil separator 82 protrudes
towards the main filter 70, it is not possible to prevent the oil
separator 82 from interfering with the main filter 70, and it is
necessary to design the filter bracket 72 to be sufficiently larger than
the oil separator 82. Meanwhile, if the structure is such that the oil
separator 82 protrudes toward the carburetor 74, the oil separator 82 can
be easily provided at a position that does not interfere with the
carburetor 74 without having to enlarge the filter bracket 72.

[0065] As shown in FIG. 9 and FIG. 10, the seal member 76 is formed with
two through holes 76a. The position of the two through holes 76a
corresponds to the position of two nipple portions 82a of the oil
separator 82. Here, the nipple portion 82a of the oil separator 82 is a
connecting opening that protrudes in a tubular shape with a rib, and the
through hole 76a of the seal member 76 is a receiving opening for
receiving the nipple portion 82a. Note that a periphery 76b, 76c of the
through hole 76a is protruding in a tubular shape by a rib at the front
and back of the seal member 76. According to the foregoing configuration,
when the filter bracket 72 is assembled to the carburetor mount 66 with
the carburetor 74 interposed therebetween, as shown in FIG. 11, the
respective nipple portions 82a of the oil separator 82 are automatically
connected to the corresponding through holes 76a of the seal member 76
from the inside of the casing 20. Subsequently, when the respective
breathing tubes 64 are connected to the through holes 76a of the seal
member 76 from the outside of the casing 20, and the oil separator 82 and
the breathing tube 64 become mutually connected via the through holes
76a. As described above, according to the structure of this embodiment,
the troublesome process of connecting the oil separator 82 to the
breathing tube 64 within the limited space in the casing 20 is no longer
required. Note that, as shown in FIG. 11, the breathing tube 64 is
connected to the through hole 76a of the seal member 76 via a joint 65.
However, the breathing tube 64 may also be connected directly to the
through hole 76a of the seal member 76 without using the joint 65.

[0066] As shown in FIG. 10, the carburetor 74 is provided with a hose
nipple 74b connected to an air vent. The distal end of the hose nipple
74b extends toward the filter bracket 72. Meanwhile, the filter bracket
72 is provided with an air vent connecting opening 72b at a position
corresponding to the hose nipple 74b. According to the foregoing
structure, when the filter bracket 72 is assembled to the carburetor
mount 66 with the carburetor 74 interposed therebetween, the hose nipple
74b of the carburetor 74 is automatically connected to the air vent
connecting opening 72b of the filter bracket 72. Accordingly, the
troublesome processing of connecting the host nipple 74b of the
carburetor 74 to the air vent connecting opening 72b of the filter
bracket 72 using a tube or the like within the limited space in the
casing 20 is no longer required.

[0067] The assembly structure of the throttle lever 30 and the switch
lever 32 is now explained with reference to FIG. 4, FIG. 12, and FIG. 13.
As shown in FIG. 4, the throttle lever 30 is supported with the shaft 34,
and is swingable around the shaft 34. The throttle lever 30 is connected
to the throttle valve of the carburetor 74 via a link 30a. Moreover, the
switch lever 32 is also mounted on the same shaft 34 in addition to the
throttle lever 30. The switch lever 32 is also swingable around the shaft
34. The switch lever 32 is connected to the choke valve of the carburetor
74 via the link 32a.

[0068] FIG. 12 shows a state where the throttle lever 30 and the switch
lever 32 are assembled to the casing main body 26, and FIG. 13 shows a
state where they are disassembled. As shown in FIG. 12 and FIG. 13, the
casing main body 26 is formed with a shaft receiving groove 26b extending
in the axial direction of the shaft 34. The shaft receiving groove 26b
retains the shaft 34 from its radial direction. Since the upper side of
the shaft receiving groove 26b is open, the shaft 34 can be easily fitted
into the shaft receiving groove 26b. In particular, the shaft 34 can be
fitted into the shaft receiving groove 26b in a state where the throttle
lever 30, a spring member 30b, and the switch lever 32 are mounted on the
shaft 34 in advance.

[0069] Here, when the user operates the throttle lever 30 or the switch
lever 32, the respective levers 30, 32 apply downward force to the shaft
34. Meanwhile, the opening direction of the shaft receiving groove 26b is
facing the upper side. Accordingly, since the opening direction of the
shaft receiving groove 26b and the direction that the shaft 34 receives
the force from the respective levers 30, 32 are mutually different, the
shaft 34 is securely retained by the shaft receiving groove 26b, and the
behavior of the respective levers 30, 32 is thereby stabilized.

[0070] In addition, with this embodiment, the shaft receiving groove 26b
is divided into two sections, and the structure is such that a space
surrounding the shaft 34 is formed between the two shaft receiving
grooves 26b. Accordingly, if the structure is such that one or more shaft
receiving grooves 26b are provided only in the lengthwise direction of a
part of the shaft 34, and space is formed around the shaft 34 in a
remaining lengthwise range, the shaft 34 that is mounted on the shaft
receiving grooves 26b can be easily removed.

[0071] As shown in FIG. 12 and FIG. 13, the filter bracket 72 is formed
with a shaft holding portion 72e at two locations. The shaft holding
portions 72c come in contact with the shaft 34 retained by the shaft
receiving grooves 26b from the opening direction of the shaft receiving
grooves 26b (upper side in this embodiment). According to this structure,
it is possible to prevent the shaft 34 retained by the shaft receiving
grooves 26b from moving or coming loose from the shaft receiving grooves
26b without having to provide a separate member for holding the shaft 34.
Moreover, as a result of the filter bracket 72 fixed to the casing main
body 26 coming in contact with the shaft 34 similarly supported by the
casing main body 26, the filter bracket 72 also functions as a support
pillar (or beam) within the casing 20, and is able to significantly
improve the rigidity of the casing 20.

[0072] As shown in FIG. 12 and FIG. 13, the casing main body 26 is
provided with a pair of shaft position determining portions 26c
respectively facing the respective ends of the shaft 34. According to
this structure, it is possible to prevent the shaft 34 retained by the
shaft receiving grooves 26b from moving in the axial direction and coming
loose from the shaft receiving grooves 26b without having to provide a
retaining member such as a circlip to the shaft 34.

[0073] The configuration of the guard 50 is now explained with reference
to FIG. 14 to FIG. 19. FIG. 14 is a diagram showing the right side of the
guard 50, FIG. 15 is a diagram showing the front side of the guard 50,
and FIG. 16 is a diagram showing the lower side of the guard 50.
Moreover, FIG. 17 is a cross section of line XVII-XVII in FIG. 14, and
FIG. 18 is a cross section of line XVIII-XVIII in FIG. 16. FIG. 19 shows
a state where a workpiece W is being cut with the engine-driven cutter
10. Here, a straight line S in the drawings shows a rotating plane of the
disk blade 12. The rotating plane S is a virtual plane where the rotating
disk blade 12 is positioned, and is a plane that is perpendicular to the
rotating axis of the disk blade 12 and which includes the disk blade 12.
However, since the disk blade 12 has a limited thickness, the rotating
plane S is defined to match the position of one end surface of the disk
blade 12. Moreover, an arrow D in FIG. 19 shows the path that the chips
of the workpiece W will scatter.

[0074] The guard 50 comprises a guard surface 90, a pair of rollers 52,
and a front leg portion 54. The front leg portion 54 is molded such that
its corner portion 54a is formed as a curved surface so that the user can
easily angle the engine-driven cutter 10. The pair of rollers 52 is
disposed coaxially with the rotating plane S of the disk blade 12
interposed therebetween, and the rotating axis thereof is parallel to the
rotating axis of the disk blade 12. The guard surface 90 is provided
between the pair of rollers 52. The guard surface 90 is a groove-shaped
curved surface formed on the guard 50, and extends along the rotating
plane S of the disk blade 12.

[0075] As shown in FIG. 18, the guard surface 90 has a tilted surface
which basically faces obliquely downward toward the front side.
Specifically, the guard surface 90 is tilted to be apart from the surface
of the workpiece as the front side position is closer to the disk blade
12. The guard surface 90 repels the chips of the workpiece that scattered
from the disk blade 12 toward the lower side of the main body 14.
Consequently, it is possible to prevent the chips of the workpiece that
scattered from the disk blade 12 in the main body 14 from being repelled
toward the user. Note that the guard 50 is formed with a plurality of
positioning protrusions 50a, and is configured so that it can be easily
assembled to the main body 14. Here, the guard surface 90 can be formed
as a surface that is free from concavo-convex or a surface with little
concavo-convex so that the chips of the workpiece are smoothly guided to
the lower side of the main body 14. However, in another embodiment,
grooves and protrusions may be intentionally provided for guiding the
chips of the workpiece to a specific direction.

[0076] The guard surface 90 has different shapes in a left side (user
side) range 90a and a right side (driving side) range 90b with the
rotating plane S as the boundary. Specifically, the guard surface 90 has
an asymmetric shape with the rotating plane S as the boundary.
Consequently, the guard surface 90 repels the chips scattered from the
disk blade 12 asymmetrically to the rotating plane S of the disk blade
12.

[0077] In particular, with the guard surface 90 of this embodiment, as
shown in FIG. 17, the normal vector N is tilted toward the rotating plane
S so as to face the rotating plane S in the entire left side (user side)
range 90a. To express this differently, in the left side (user side)
range 90a of the guard surface 90 formed in a groove shape, the depth
becomes narrow as it becomes separated from the rotating plane S.
Accordingly, in the left side (user side) range 90a, the chips that
scattered from the disk blade 12 are repelled toward the rotating plane
S. Specifically, the chips that scattered from the disk blade 12 to the
left side (user side) can be repelled toward the right side (driving
side). Consequently, many of the chips that scattered from the disk blade
12 are repelled to the right side (driving side) of the main body 14. The
user can use the engine-driven cutter 10 comfortably without being
obstructed with the chips as a result of positioning oneself on the left
side (user side) as the opposite side.

[0078] The shape of the guard surface 90 described above is an example,
and the shape of the guard surface 90 is not limited thereto. The shape
will suffice so as long as a majority of the chips that scattered from
the disk blade 12 can be repelled to the right side (driving side) of the
main body 14, and, for example, the angle, depth, and area of the guard
surface 90 may be changed between the left side (user side) range 90a and
the right side (driving side) range 90b.

[0079] As shown in FIG. 19, the user can move the engine-driven cutter 10
along the surface of the workpiece W in a state of causing the pair of
rollers 52 to come in contact with the surface of the workpiece W and
angling the engine-driven cutter 10 towards the surface of the workpiece
W. Here, even if there is an obstacle (for instance, a fragment of the
workpiece W or a protrusion of the workpiece W) on the surface of the
workpiece W, it is possible to go over the obstacle by angling the guard
surface 90. In particular, with the engine-driven cutter 10 of this
embodiment, the pair of rollers 52 are used as the fulcrum, and, even
when the engine-driven cutter 10 is fully angled towards the surface of
the workpiece W (state of FIG. 19), the guard surface 90 is tilted to
become separated from the surface of the workpiece W as it approaches the
disk blade 12 (front side). Specifically, a height T from the surface of
the workpiece W to the guard surface 90 becomes higher as it approaches
the disk blade 12 (front side). According to this structure, regardless
of the angle when the engine-driven cutter 10 is angled towards the
surface of the workpiece W, it is possible to go over the obstacle
existing on the surface of the workpiece W based on the tilt of the guard
surface 90.